Adjustable inductance coils



Dec. 8, .1959 A. DONAVY ADJUSTABLE mucmcr: cons 2 Sheets-Sheet 1 FiledOct. 23. 1956 FIG.2

FIG.

PIC-5.4

FIG. 3

Dec. 8, 1959 A. DONAVY ADJUSTABLE mnucnmca cons 2 Sheets-Sheet 2 FiledOct. 23, 1956 FIG.6'

. "saturation The present invention relates to inductance coils, andmore particularly to coils of the type comprising two series-connectedwindings, wherein the inductance may I be varied by modifying thedirection of the magnetic flux produced by one of the windings withrespect to the direction of the magnetic flux produced by the otherwinding. The invention more particularly relates to coils of the ftypein which the two windings are supported by two U-shaped ferro-magnetiecores arranged in such a manner that the flux produced by each windingpasses into the coreof the other winding.

In such inductance devices, the two cores are usually rotatable one withrespect to the other, in order to proyide a varying gap therebetween soas to vary the inductance of the coil. The construction of suchinductance devices is somewhat complex and delicate, sliding contactsbeing needed vfor connection of the rotating winding with the outsidecircuits.

Therefore, it is an object of the invention to provide an inductancedevice of easy and dependable construction, comprising twoseries-connected fixedwindings and,

therefore, free of the above disadvantages.

The inductance device according to the invention comprises a pair offerro-magnetic cores having their pole pieces secured on a flat piece offerro-magnetic material, and magnetizing means adapted to producemagnetic of said flat piece along a varyingydirection thereof- Thevariationof the inductance is eifected by modifying said direction.

The invention will be better understood from the following descriptionwhen read in conjunction with the aceompanying drawings, in which;

Fig. 1 shows, schematically, a side view of a coil according to theinvention;

Fig. 2 is a perspective view of the essential components of the coilrepresented in Fig. 1 with parts broken off;

Figs. 3 and 4 illustrate the operation of the"'coil of Figs. 1 and 2;

Fig. 5 is a perspective view illustrating a modified embodiment of theinvention;

Fig. 6 is a diagrammatic, partially sectional side view, of anotherembodiment of the invention;

Fig. 7 is a front view of certain parts of the coil illustrated in Fig.6; and

Fig. 8 is a diagram illustrating still another embodiment of theinvention.

Referring particularly now to Figs. 1 and 2, a coil is shown comprisingtwo series-connected windings 1 and 2, wound, respectively, on twostationary cores 3 and 4 of ferro-magnetic material. In thenon-limitative embodiment described, these two cores 3 and 4' are in theshape of a U with two equal branches, the end faces of which, 5 and 6,and 7 and 8 respectively, are fiat and secured to a disc 16 offerro-magnetic material, at the respective ends of two diameters of thedisc 16 perpendicular to each other, the assembly comprising the coresand the disc United States Patent 0 being supported by a frame 17, ofnon-magnetic material. A permanent magnet 18 is provided, the polepieces 19 and 20 of which are applied on the periphery of the disc 16,at two directly opposed points thereof, said magnet being mounted insuch a manner as to rotate about the axis YY' of the disc 16. In ordernot to interfere with the rotation of the magnet 18, feeding wires 22and 23 for the winding 2 are threaded through small holes provided inthe disc 16.

The magnet 18 is adapted to effect saturation of the disc 16, along adiameter joining the poles 19 and 20 of the magnet 18. Thus, when themagnet 18 is oriented as shown in Fig. 3, the disc 16 becomes saturatedalong diameter AB; the flux of the coil then extends over a closed pathincluding sections 26 and 27 of the disc 16, said sections 26 and 27having a much higher magnetic permeability than that of the saturatedsections 28 and 29; under these conditions, the magnetic circuit of thecoil follows the closed path illustrated by the line 3131' and,consequently, the resulting flux of the coil is the sum of the fluxesproduced by windings land 2. When the magnet 18 is oriented as shown inFig. 4, the disc 16 becomes saturated along diameter A B; the flux ofthe coil, which then passes through the sections 28, 29 and follows theclosed path shown by line 3232' is thus the difference between thefluxes generated by both windings 1 and 2.

It is thus apparent that the resultant flux in the magnetic circuit ofthe coil may considerably vary. ,The range covered by the inductance isthus very wide in the case illustrated; in Fig. 3, wherein the resultantflux is maximum, the value of the inductance is maximum, whereas it isminimum in the case of Fig. 4, where the resultant flux is minimum, andit has an intermediate value if the magnet 18 is in an intermediateposition between those shown in Figs. 3 and 4.

In the alternative embodiment of Fig. 5, both cores 3 and 4 arepositioned on the same side of the disc 16, the magnet 18 being placedon the other side. In this embodiment, the continuous rotation of themagnet 18 is possible, without requiring any connecting Wire to passthrough the disc 16.

The same result is also obtained in the embodiment illustrated in Figs.6 and 7. In this case, the cores 3 and 4 are located on opposite sidesof the disc 16, and the magnet 18 has a shape enabling it to be disposedin the plane of the disc 16. The wire 33 connecting the windings 1 and 2then passes beyond the periphery of the magnet 18 and does not interferewith the rotation thereof.

In the modified embodiment represented in Fig. 8, instead of a rotatingmagnet, two stationary electro-magnets 34 and 35 are provided which havetheir poles applied on the periphery of the disc 16; the poles 36 and 37of the first magnet 34 engage the ends of the diameter AB, and the poles38 and 39 of the second magnet 35 engage the ends of the diameter A B,perpendicular to AB. Diameters AB and A B are, preferably, orientedaccording to the bissectrices of the angles formed by the diameters MNand M N which pass through the junctions of the cores 3 and 4 with thedisc 16. The windings 41 and 42 of the electro-magnets 34 and 35 are fedby direct current supplied through an adjusting device, such as apotentiometer 43, which enables the intensity of the current to beadjusted in each of said windings. When the sliding contact 44 of thepotentiometer 43 is on the end point 46, the electro-magnet 34 is in aposition of maximum energization; the disc 16 is thus saturated alongthe diameter AB, realizing the conditions described in connection withFig. 3. When the sliding contact 44 is on the other end point 47, theelectro-magnet 35 is in a position of maximum energization,electro-magnet 35 being non energized; disc 16 will then be saturatedalong the direction of diameter AB, realizing the conditions illustratedin Fig. 4. With the sliding contact 44 at a position intermediatebetween end points. 46 and 47,21

condition intermediate between those shown in'FigS. 3 and 4 will bereached, and consequently, the coil will present an inductanceintermediate betweenthernaximum value corresponding to the positionshown in Fig. 3- and the minimum value corresponding to the position.shown in Fig. 4.

,It is to be understood that the invention is in no Way limited by theembodiments illustrated,, and that many modifications may be devisedwithout departing from the scope of the invention.

For instance, the permanent'magnet 18 of theembodi- ,ment shown in Figs.1 through 7 may be replaced by an electro-magnet; on the other hand, aferrite material may be utilized for the cores 3 and 4 and the disc 16.Air

. gaps may also be provided in the magnetic circuit of the producingmagnetic saturation of saidflat piece along a variable directionthereof.

2. A variable inductance comprising a pair. of ferro ;magnetic coreseach having two pole pieces; an inductance coil wound on each of saidcores; a disc of ferromagnetic material, on which said pole pieces, are.secured in quadrature, said pole pieces being perpendicular to said discand said cores substantially spanning said disc and magnetizing meansfor producing magneticsaturation of said disc along a diameter thereof,thea gular position of which is variable.

3. A variable inductance device according to claim 2, in which saidferro-magnetic cores are U-shaped.

4. A variable inductance device according to claim 2, in which saidferro-magnetic cores are respectively located on the two faces of saiddisc.

5.. A variable inductance device according to,,claim 2, in which saidferro-magnetic cores are both located on the same face of said disc, intwo planes perpendicular to said disc and at right angles one withrespect to the other.

6. A variable inductance device comprising a pair of ferro-magneticcores each having two pole pieces; an inductance coil wound on each ofsaid cores; a disc of ferro-magnetic material on which said pole piecesare secured in quadrature, said cores substantially spanning said disc,and a permanent magnet having its pole pieces in contact with theperiphery of said disc at the ends of one diameter thereof, saidpermanent magnet being rotatable about the axis of said disc.

7. A variable inductance'device according toclaim 6, in which two coilsare respectively wound around said cores and connected to feeding wirespassing through apertures provided in said disc.

8. A variable inductance device according to claim 6, in which saidpermanent magnet is perpendicular to the plane of said disc.

9. A variable indutance device according to claim 6, in which saidpermanent magnet is located in the; plane of said disc, around theperiphery thereof.

10. A variable inductor comprising a pair of ferromagnetic cores eachhaving two pole pieces; an inductance coil wound on each of said cores;a flat disc .of ferro-magnetic material On which said pole pieces aresecured in quadrature, respectively at the ends of two perpendiculardiameters thereof, said pole pieces being perpendicular to the surfaceof said flat piece and. said cores-substantially spanning said flatpiece; andmagnetizing means, comprising a pair of stationaryelectromagnets having their pole pieces in contact with the periphery ofsaid flat disc, respectively, at the ends of two I perpendiculardiameters thereof, for producing magnetic saturation of said flat discalong a variable diameter thereof.

11. A variable inductor according to claim 10, in which said twoperpendicular diameters joining the pole pieces of the electro-magnetsare oriented according to the, bissectrices of said two perpendiculardiameters joining the pole pieces of the cores.

12. A variable inductor according to claim 10, in which saidelectro-magnets comprise adjustable energizing means.

References Cited in the file of this patent UNITED STATES PATENTS2,126,790 Logan Aug. 16, 1938 2,617,090 Ogle Nov. 4, 1952 2,762,020Gordon Sept. 4, 1956 2,831,157 Grayson Apr. 15, 1958 FOREIGN PATENTS874,663 France May 18, 1942 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Alain Donavy Patent should read as corrected below.

Column 1.111% 42, 44., and 47, and. column 4, lines 1, l0, l4, and 17,strike: out "davie e", each occ'unstrcence Signed and sealed E3115 dayof May 1960.,

Attest:

KARL I-JI, ROBERT C. WATSON Attesting Officer Commissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,9l,l4 December 8, 1959 Alain Donavy It is hereby certified that errorappears in the-printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3, lines 42, 44., and 4.7, and column 4, lines 1, l0, l4, and 17,strike out "device", each occurrence.

Signed and sealed this day of May 1960.,

(SEAL) Attest:

KARL H, Attesting Oificer ROBERT C. WATSON Commissioner of Patents

